1. Field of the Invention
The present invention relates to a carbon electrode and a process for preparing it.
2. Description of the Prior Art
Carbonaceous materials such as graphite have pores with a porosity of less than 30% by volume, and are susceptible to air permeable osmosis. Accordingly, when carbon material is used as an electrolytic electrode, oxidation is caused not only on the surface of the carbon material but also in the pores resulting in local erosion. Consequently, excessive consumption of the carbonaceous material is caused by the breakdown of the structure of the carbon particles.
For example, it has been reported that the inner pores, having diameters of 2,500-70,000 A.degree., of a graphite anode used for the electrolysis of brine cause inner consumption of the electrode.
In past attempts to overcome this disadvantage the inner pores of electrolytic carbon electrodes have been filled and/or coated by impregnation-hardening methods using drying oils such as linseed oil and tung oil, chlorinated oils of said drying oils, chlorinated naphthalene, styrene-divinylbenzene type resins and the like and by impregnation-carbonizing methods using carbonized high molecular weight material such as pitch and the like.
However, since linseed oil is not easily hardened in the inner pores of a carbon electrode, a long hardening time is required. Also, chlorinated naphthalene is toxic. Moreover, most of the conventional thermosettable resins have inferior adhesiveness to the carbon material.
In the impregnation-carbonizing method using pitch, a large size apparatus is required and the effectiveness of the treatment is relatively low. In any case, it is difficult to coat the inner wall of the pores by the conventional methods, whereby excess consumption of the carbon electrodes by inner oxidation cannot be prevented. Consequently, it would be most desirable to have a technique for preventing the inner oxidation of carbon electrodes.